Observations on step bunching for the layer perovskite (C 3H 7NH 3) 2MnCl 4 using a compound holographic interference and conventional microscope

Abstract

A compound microscope is described, which consists of a holographic interference microscope and a conventional microscope. Both systems can be optimized independently for fringe and image contrast, respectively. The system combines (i) the highly corrected image and long free working range of microscopy with (ii) the large vertical resolution and overall spatial information of interferometry and with (iii) the increased depth of imaged volume and potentialities for time sequential observations of holography. The coherence of the light enables interference microscopy of crystal growth from a bulk solution. Holographic magnification and interference systems are reviewed briefly, together with their applications to crystal growth. With the compound microscope the crystal surface of the layer perovskite (C 3H 7NH 3) 2MnCl 4 has been recorded during growth and dissolution from an aqueous bulk solution. Refractive indices of crystal and solution, Miller indices and stability of high index (or vicinal) faces, and height, slope, profile and life time of step bunches have been investigated. During dissolution, grooves appeared on the {001} platelet faces along the a- and b-directions, penetrating inwards from the edges. At low supersaturations etch pits consisted of a pair of similar, intersecting grooves. Both optical subsystems of the compound microscope proved to be indispensable for the description of complex phenomena, such as step bunching. On their own, they presented incomplete and even misleading information.